Device for supplying fluid under pressure to at least two utilisation circuits

ABSTRACT

A device for supplying fluid under pressure to at least two utilization circuits, each being connected to be supplied by a group of pumps comprising at least one pump and one delivery pipe, one of said groups of pumps being of the constant-delivery type, at least one other of said groups of pumps being of the variable-delivery type, the input shafts of the groups of pumps being connected to a single driving shaft, said supply device comprises at least one power regulator including a first jack whose piston is coupled to a member for controlling the delivery of said other group and is subjected to the opposing actions of a resilient member and of the pressure of fluid in the delivery pipe of said other group of pumps, a second jack whose piston is connected to the member for controlling the delivery of said other group and delimits with the cylinder of said second jack a chamber which is connected to the delivery pipe of the one group of pumps by a connecting pipe, a laminar hydraulic restriction disposed in the connecting pipe, the piston of the second jack being subject to the opposing actions of the resilient member and the pressure of fluid in the chamber, and a second restriction, having a hydraulic resistance which is variable in dependence on the position of the piston of the second jack in its cylinder and through which said chamber communicates with an enclosure at substantially zero pressure.

Unite tats Bacquie et aI.

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[ DEVICE FOR SUPPLYING FLUID UNDER PRESSURE TO AT LEAST TWO UTILISATION CIRCUITS Inventors: Serge B. Bacquie, rue de Picardie,

60610 Lacroix-Saint-Ouen; Louis E. Martin, Residence Brichebay, 60300 Senlis, both of France Filed: Sept. 13, 1973 Appl. No.: 396,768

[56] References Cited UNITED STATES PATENTS 4/l97l l-lufeld et a1. 60/422 5/1971 Abe et a1. 60/429 Primary Examiner-Edgar W. Geoghegan Attorney, Agent, or FirmLewis H. Eslinger; Alvin Sinderbrand [57] ABSTRACT A device for supplying fluid under pressure to at least two utilization circuits, each being connected to be supplied by a group of pumps comprising at least one pump and one delivery pipe, one of said groups of pumps being of the constant-delivery type, at least one other of said groups of pumps being of the variabledelivery type, the input shafts of the groups of pumps being connected to a single driving shaft, said supply device comprises at least one power regulator including a first jack whose piston is coupled to a member for controlling the delivery of said other group and is subjected to the opposing actions of a resilient member and of the pressure of fluid in the delivery pipe of said other group of pumps, a second jack whose piston is connected to the member for controlling the delivery of said other group and delimits with the cylinder of said second jack a chamber which is connected to the delivery pipe of the one group of pumps by a connecting pipe, a laminar hydraulic: restriction disposed in the connecting pipe, the piston of the second jack being subject to the opposing actions of the resilient member and the pressure of fluid in the chamber, and a second restriction, having a hydraulic resistance which is variable in dependence on the position of the piston of the second jack in its cylinder and through which said chamber communicates with an enclosure at substantially zero pressure.

11 Claims, 8 Drawing Figures DEVICE FOR SUPPLYING FLUID UNDER PRESSURE TO AT LEAST TWO UTILISATION CIRCUITS When a hydraulic circuit is fed by a plurality of pumps, the power of the motor driving the pumps should be selected to be at least equal to the sum of the input powers of the pumps in question, if these pumps are liable to be operated simultaneously under conditions of maximum power.

This leads to over-dimensioning of the driving motor if one or more of the pumps has a low proportion of use.

This is particularly the case in certain public works machines, in which the operations, translation of the machine and actuation of the equipment, are effected by different pumps.

Excellent facility in handling, and consequently a maximum speed of displacement are required of the machine: the pumps of translation (for example a double body pump with variable cubic capacity and power regulation by summation of the pressures) will then have characteristics such that they use the maximum power of the driving motor (for example 100 hp).

Since the equipment is not actuated, the machine will be displaced at maximum speed, the fluid under pressure being supplied by the double body pump of variable cubic capacity.

On the other hand, when the machine, having ended its translation from one, e.g., a loading point to another, e.g., an unloading point or vice versa, needs to exert a maximum effort with its equipment, at low speed, or even when stopped, it would be desirable for the pump having a constant cubic capacity and feeding the equipment circuit to be able to have at its disposal, with priority, a high power equal to the power of the motor driving the pumps, but reduced by the power necessary to drive the double body pump with a variable cubic capacity in accordance with a constant power curve, the value of which would be reduced automatically, for example from 100 hp to 40 hp.

In this manner, it would be possible to have 100 hp. available for the translation and 60 hp. for the equipment, using a driving motor for the pumps delivering an output power of only 100 h.p., instead of the 160 hp. necessary with a conventional device and under the same conditions of operation.

It is the object of the invention to propose a novel de vice enabling a large economy to be effected, both in the construction of the machine and in it running costs, the operational performance being retained.

According to one aspect of the invention there is provided a device for supplying fluid under pressure to at least two utilization circuits, each being connected to be supplied by a group of pumps comprising at least one pump and one delivery pipe, one of said groups of pumps being of the constant-delivery type, at least one other of said groups of pumps being of the variabledelivery type, the input shafts of the groups of pumps being connected to a single driving shaft, said supply device comprises at least one power regulator including a first jack, the cylinder of which is rigidly connected to the body of the pumps of said other group and the piston of which is coupled to a member for controlling the delivery of said other group and is subjected to the opposing actions of a resilient member and of the pressure of fluid in the delivery pipe of said other group of pumps, a second jack, the cylinder of which is rigidly connected to the body of the pumps of said other group and the piston of which is connected to the member for controlling the delivery of said other group and delimits with the cylinder of said second jack a chamber which is connected to the delivery pipe of the one group of pumps by a connecting pipe, a laminar hydraulic re striction disposed in the connecting pipe, the piston of the second jack being subject to the opposing actions of the resilient member and the pressure of fluid in the chamber, and a second restriction, having a hydraulic resistance which is variable in dependence on the position of the piston of the second jack in its cylinder and through which said chamber communicates with an enclosure at substantially zero pressure.

According to another aspect of the invention there is provided a device for supplying fluid under pressure to at least three utilization circuits, each being connected to be supplied by a group of pumps comprising at least one pump and one delivery pipe, one of said groups of pumps being of the constant-delivery type, and each of the other two groups of pumps being of the variabledelivery type, the input shafts of the groups of pumps being connected to a single driving shaft, and two power regulators are connected, a first power regulator being connected to a member for controlling the delivery of a first of the other two groups of pumps, and a second power regulator being connected to a member for controlling of pumps, wherein each regulator comprises three jacks, the pistons of which are connected to the member for controlling the delivery of the corresponding group of pumps, and each of which delimits a chamber for fluid, the effects of which are opposed to that of a resilient member, a first one of the chambers of each of the regulators communicates with the delivery pipe of one of the other groups of pumps, a

second one of the chambers of each regulator commu nicates with the delivery pipe of the other one of the other groups of pumps, and a third one of the chambers of each of the regulators is connected by a connecting pipe to the delivery pipe of the one group of pumps, a first laminar hydraulic restriction is disposed in the connecting pipe, and two second restrictions, each having a hydraulic resistance which is variable in dependance on the position of the piston of each of the jacks, called second jacks, delimiting the third chambers, through which a respective one of the third chambers communicates with an enclosure at substantially zero pressure.

The device may comprise a fourth utilization circuit connected to be selectively supplied by a second group of constant-delivery pumps, comprising at least one pump and one delivery pipe in which there is disposed a distributor having at least two positions for bringing said delivery pipe of the second group of constantdelivery pumps into communication, in one position, with the fourth utilization circuit by means of a secondary delivery pipe and, in another position, with a fluid reservoir, and a secondary connecting pipe which connects said secondary delivery pipe to the third chamber of one of the two regulators, a non-return valve being disposed in the connecting pipe connected to said third chamber, between the third chamber and the laminar hydraulic restriction disposed in said connecting pipe so as to permit the passage of fluid only from said laminar hydraulic restriction to said third chamber.

It may be an advantage to dispose a pressure-adjusted valve in the or each connecting pipe between its connection to the delivery pipe of the one group of pumps and the laminar restriction, the valve being controlled by the pressure of fluid in the delivery pipe.

The laminar restriction is preferably adjustable, comprising a rod provided with helical threads and disposed in a cylindrical bore, and means for moving the rod in the bore to vary the length of the thread situated in said bore.

The or each second restriction may be formed by a groove formed in the cylindrical face of the piston of the second jack, corresponding to said second restriction, a length of said groove, which is variable in dependence on the position of said piston, being disposed opposite a wall of the cylinder in which said piston is slidably mounted. This groove is preferably helical.

The invention will be better understood from the following description of embodiments thereof, given below by way of example only, with reference to the accompanying drawings.

In the drawings:

FIG. 1 is a diagrammatic view, partially in section, of an embodiment of a supply device according to the invention;

FIG. 2 is an entirely diagrammatic view of the supply device of FIG. 1;

FIGS. 3 and 4 are graphs illustrating the operation of the supply device of FIGS. 1 and 2;

FIG. 5 is an entirely diagrammatic view of a modification of the device of FIG. 1;

FIG. 6 is a diagrammatic view of another embodiment of a supply device according to the invention;

FIG. 7 is a graph illustrating the operation of the supply device of FIG. 6; and

FIG. 8 is a diagrammatic view of a further embodiment of a supply device according to the invention.

In the embodiment illustrated with reference to FIGS. 1 to 4, a single engine 1, as shown a diesel engine, has its output shaft 2 connected to a single driving shaft 3 by means of a coupling 4. The shaft 3 actually constitutes the driving shaft of a variable-delivery pump 5, of which the member controlling the delivery is indicated at 6 as being a lever articulated at 7. A pinion 8, rigidly connected to the shaft 3, cooperates with a pinion 9, rigidly connected to the driving shaft 10 of a constant-delivery pump 11. The variable-delivery pump 5 is connected by a suction pipe 12 to a fluid reservoir 13, and by a delivery pipe 14 to a utilization circuit 15. The constant-delivery pump 11 is connected by a suction pipe 16 to the reservoir 13 and by a delivery pipe 17 to a utilization circuit 18.

It should be noted that it is possible to provide groups of pumps, of variable delivery type and constant delivery type respectively, instead of each of the pumps 5 or 11. In the embodiment illustrated, the utilization circuit is the supply circuit for the hydraulic motors for driving a public works machine in translation, and the utilization circuit 18 is the supply circuit for the jacks actuating the working equipment of the machine. The variable-delivery pump 5 may be of any known type, for example a so-called axial-piston pump, the cylinders of which are formed in a barrel and are parallel to one another and to the axis of rotation of said barrel, the pistons bearing against a plate which can be inclined in relation to said axis of rotation. This plate constitutes the member 6 for controlling the delivery of the pump.

A power regulator 19 is provided to control the position of the control member 6 and so ensure the regulation of the delivery of the pump 5. This regulator consists ofa body 20 which is rigidly connected to the body of the pump 5 and in which there are formed three cylindrical bores 21, 22 and 23. A piston 24 is mounted for sliding in the bore 21 and bears against another piston 25 which is mounted for sliding in the bore 22. The piston 25 is provided with a helical groove 26 in its cylindrical face. The control member 6 is articulated about a pin 27 on the end of the piston 25. This end of the piston 25 bears against a push-rod 28, three springs 29, 30 and 31, having unequal and decreasing initial lengths, being interposed between the pushrod 28 and the body 20 of the regulator.

Two chambers 32 and 33 are formed in the body 2 and contain respectively that end of the piston 24 opposite that which is bearing against the piston 25, and that end of the piston 25 opposite that which is bearing against the push-rod 28. A length 10 of the piston 25 provided with the helical groove 26 lies within the cylindrical bore 22 and thus a restriction 34 is formed between the chamber 33 and a chamber provided by the reservoir 13.

A rod 35 is screwed into the body 20 by means of a fixing thread 36 and is locked in position by a nut 37. The end of this rod is provided with helical threads 38 having a smaller internal diameter than the diameter of the bore 23 and is disposed in the bore over a length la. Two chambers 39 and 40 are separated by this length of the threaded rod 35. The clearance formed between the threads 38 on the rod 35 and the bore 23 constitutes a laminar restriction 41.

A pipe 42 connects the chamber 32 to the delivery pipe 14 of the variable-delivery pump 5. Similarly, a pipe 43 connects the chamber 39 to the delivery pipe 17 of the constant-delivery pump 11, and a pipe 44 in terconnects the chambers 33 and 40. The pipes 43 and 44 may also be regarded as forming a single connecting pipe connecting the delivery pipe 17 to the chamber 33, a laminar restriction 41 being disposed in this connecting pipe. Finally, a pipe 45 connects the outlet of the restriction 34 to the reservoir 13.

It will be noted that the assembly of the piston 24, the bore 21 and the chamber 32 can be regarded as a first jack, and the assembly of the piston 25, the bore 22 and the chamber 33 can be regarded as a second jack.

FIG. 2 does not show any further features of the device illustrated in FIG. I, but is given solely for the purpose of making clear the symbolic representation used, particularly that relating to the restrictions 34 and 41.

FIG. 3 represents the curve 46, actually close to a straight line, indicating the variation in the delivery 0c of the constant-delivery pump 11 depending on the pressure Pc of the fluid in the delivery pipe 17. Three operational points F1, F2 and F3 have been marked:

the point Fl corresponding to the case where the driving power of the pump 11 is zero;

the point F3 corresponding to the case where the driving power of the pump 11 is maximum and equal to hp. in the example selected; and

the point F2 corresponding to an intermediate case between F1 and F3, for which the driving power of the pump 11 is equal to half the maximum power, hence to 30 h.p.

FIG. 4 represents the variation in the delivery Qv of the variable-delivery pump 5 depending on the pressure Pv of the fluid in the delivery pipe 14. Three curves C1, C2, C3 represent three modes of operation corresponding respectively to the abovementioned points F1, F2, F3. They are actually hyperbolas, on each of which the product Pv X Qv is constant and equal to the driving power of the vairable-delivery pump 5. In the example selected, the powers are equal to 100 hp, 70 hp. and 40 hp. for the operations corresponding respectively to the curves C1, C2 and C3. It may also be specified that the diesel engine 1 develops a maximum power of 100 hp. and that, in order to simplify the explanation, the mechanical and hydraulic losses of power, particularly in the meshing of the pinions 8 and 9 and in the driving of the pumps will be ignored hereafter.

FIG. 5 illustrates diagrammatically a modification of the embodiment of FIG. 2. A pressure-adjusted valve 47 is disposed in the pipe 43 between the connection of the pipe 43 to the delivery pipe 17 and the adjustable laminar restriction 41. The valve 47 is controlled by the pressure of the fluid contained in the delivery pipe 17, by means of a pipe 48.

FIG. 6 illustrates another embodiment according to the invention comprising two variable-delivery pumps 5a and 5b. The same reference numerals are used in FIG. 6 for parts corresponding to parts of the embodiments of FIGS. 1 to 5.

In this embodiment the shaft 3 derives the constantdelivery pump 11 directly. A pinion 8a is rigidly connected to this shaft 3 and cooperates with a pinion 9a which is rigidly connected to the driving shaft 10a of a first variable-delivery pump 5a, and with a pinion 9b which is rigidly connected to the driving shaft 10b and a second variabledelivery pump 5b, the characteristics of which are identical, in this case, to those of the pump 5a. The pumps 5a, 5b are connected to the reservoir 13 by suction pipes 12a, 12b, and to two utilization circuits 15a, 15b by delivery pipes 14a, 1412 respectively.

Each pump 5a, 5b is equipped with a power regulator 19a, 19b, similar to the regulator 19. Regulator 19a comprises a restriction 34a, a chamber 33a and two pistons Hub and 2411a, the ends of which lie in chambers 32ab, 3211a. Regulator 19b comprises restriction 34b, chamber 33b, and two pistons 24ba and 24bb, the ends of which lie in chambers 32ba, 32bb. Pipe 42a, branched off from the delivery pipe 14a, splits into two pipes 49a and 50a connected to the chambers 32aa and 32ba respectively, and pipe 42b, branched off from the delivery pipe 14b, splits into two pipes 49b and 50b connected to the chambers 32ab and 32bb respectively. Each regulator is connected to a respective one of the members 6a, 6b for controlling the delivery of each of the variable-delivery pumps 5a, 5b. The Charm bers 33a, 33b are connected by pipes 44a, 44b to the outlet of the adjustable laminar restriction 41.

The graph of FIG. 7 represents a curve C relating to a given operational condition and illustrating the variation in the delivery Qv of either of the two variabledelivery pumps 54 and 5b which in this case are identical, depending on the sum of the pressures Pva and Pvb of the fluid contained in the delivery pipes 141a and 14b. It will be understood that, as illustrated in FIG. 6, the restrictions 34a and 34b are identical as are the pistons 2411a, Mab, Z-tlba and 24bb, and that therefore the two pumps 5a, 5b have the same delivery Qv.

FIG. 8 illustrates another embodiment according to the invention which includes many of the parts of the device illustrated in FIG. 6 but in which the single laminar restriction 41 and the single pressure-adjusted valve 47 of FIG. 6 are replaced respectively by two identical laminar restrictions 41a, 41b, and by two identical pressure-adjusted valves 47a and 47b, and in which provision is made for the supply of fluid to a fourth utilization circuit 53a and a fifth utilization circuit 53b by means of another constant-delivery pump 51.

It will be noted that a supplementary pinion 54 is rigidly connected to the shaft 2 and meshes with a pinion 55, itself rigidly connected to the driving shaft 56 of the constant-delivery pump 51. This pump 51 is connected by a suction pipe 57 to the reservoir 13 and delivers fluid to pipe 58. Two pipes 64a, 64lb extend the pipe 58, being branched off in parallel and. being connected respectively to a two-position distributor 63a, 63b controlled by a pedal and preferably being of the progressive type. Two pipes 64a, 64b connect the distributors 63a, 63b to the fourth utilization circuit 53a and to the fifth utilization circuit 53b respectively. A pipe 65 connects the pipe 62b to a pressure-adjusted valve 59, controlled by the pressure of the fluid contained in the pipe 62b through a pipe 60. This pressure-adjusted valve 59 is further connected to the reservoir 13 by a pipe 61.

The distributors 63a, 63b, in their first positions bring the pipes 62a, 64a and 62b, 64b respectively into communication and, in their second positions, close communication between the pipes 62a, 64a and 62b, 64b. A pipe 66a connects the pipe 640: to the chamber 33a, and a pipe 66b connects the pipe 64b to the chamber 33b.

Two pipes 43a, 43b, similar to the above-mentioned pipe 43, are connected to the delivery pipe 17 of the constant-delivery pump 11, and are each connected to a respective pressure-adjusted valve 47a, 47b. A respective restriction 41a, 41b is connected to the outlet of a respective pressureadjusted valve 47a, 47b and is similar to the restriction 41 previously described; a respective non-return valve 52a, 52b is connected to the outlet of a respective restriction 41a, 41b. Finally, a respective pipe 44aa, 4411b, similar to the abovementioned pipes 44a, 44b, connects the outlet of a respective non-return valve 52a, 52b to a respective chamber 33a, 33b. In the embodiment illustrated the utilization circuits 53a, 53b consist of the hydraulic feed circuits for one direction of the machine, the one corresponding to a change in direction of the machine towards the right, the other to a change in direction of the machine towards the left.

The modes of use of the above-described supply devices will now be explained together with the advantages obtained by adopting said devices.

First of all, the operation of the device described with reference to FIGS. 1 and 2 will be examined. The fluid in the pipe 43 passes through the Iaminar restriction 41. The rate of flow or delivery q of this fluid has the value:

q K Ap/la in which K is a constant and Ap is the drop in pressure of the fluid between the chambers 39 and 40 This fluid,

whose rate of flow q is controlled by the value of the restriction 41, flows through the pipe 44 to the chamber 33 and has an effect tending to displace the piston 25 against the action of the or one of the springs 29, 30, 31. Similarly, the fluid flowing through the pipe 42 into the chamber 32 has the effect of tending to displace the piston 24, and hence the piston 25, against the action of the or one of the above-mentioned springs.

Fluid contained in the chamber 33 escapes from this chamber at the same rate of flow q referred to above, and does so through the variable restriction 34 formed by the length 10 of the grooved piston 25 situated in the bore 22. At the restriction 34, the rate of flow q therefore has the value:

and approximately in which K is a constant and p is the difference in pressure of the fluid contained in the chamber 33 and in the pipe 45. Variation in the value of the hydraulic resistance 34, depending on 10, may be provided by a variation in the depth of the groove 26. Corresponding to a given length In there is a given position of the member 6 for controlling the delivery of the variable-delivery pump 5, for example of the supporting plate for the pistons of the axial-piston pump, in the case where such a pump is selected. Combining the formulae (1) and (2) gives:

fluid contained in the delivery pipe 17 of said pump, it is also possible to write:

p Pc Ap which accounts for the action of the restriction 41, and

We P Qc which accounts for the power of the pump 11 which,

as is well known, is equal to the product of the pressure by the delivery.

The combination of the formulae and (6) enables P0 to be expressed depending on p. Moreover, since Qc is constant and K is a constant, it is found that:

p=K X We The pressure p which acts on the piston 25 is therefore, approximately, proportional to the power We of the constant-delivery pump 11, likewise the displacement of the piston 25 depends thereon and hence the displacement of the control member 6. Now, the characteristics of the springs 29, 30 and 31 are such that the displacements of the piston 24 and hence of the piston 25 under the action of the pressure of the fluid in the chamber 32 maintain the power Wv of the variabledelivery pump 5 constant on one of the curves C,, C, or C in FIG. 4, or on a similar intermediate curve. The action of the fluid in the chamber 33 on the piston 25 only displaces this, and consequently the control mem her 6, through a distance which corresponds to subtraction of the power We of the constant-delivery pump 11 from the power Wv of the variabledelivery pump 5, this subtraction being effected automatically for each value of We, and enabling the variable-delivery pump 5 to continue to operate at a constant power lower by the value We than the operating power would be in the absence of the constant-delivery pump 11.

It will be understood that the power to be subtracted, equal to We, can be regulated by modifying the value of Ap. In order to do this, it is sufficient to screw the rod 35 in or out to a greater or lesser extent to select a length la of the desired value.

In this manner, it is possible, for example, to obtain the following three modes of operation:

We O and Wv 100 hp, when the machine is in free translation at maximum speed and none of its equipment is actuated; these are the point F and the curve C,;

Wc 60 hp. and Wv 40 hp. when, although the machine is continuing its translation, its equipment is actuated with priority. A temporary reduction in the speed of translation is then accepted in order to actuate the equipment with priority. These are the point F and the curve C We 30 hp. and Wv hp, which is an intermediate mode of operation between the first two and corresponds to the point F and the curve C In every case, the sum of the powers Wv and We is maintained at most equal to the power of the engine 1, in this case the hp. diesel engine, because, as has been observed, the power We necessary for driving the constant-delivery pump 11 is subtracted from the power Wv.

It may, however, happen that the maximum power of the variable-delivery pump 5 is lower than the power of the engine 1. In this case, it is necessary to avoid reducing the part of the power of the engine still available for driving the constant-delivery pump 11. In order to achieve this object, it is necessary to adopt the device of FIG. 5. In the embodiment of FIG. 5, the engine 1 can develop a maximum power of l20 h.p., the variable-delivery pump 5 only takes up a maximum power of 100 hp, and the maximum power of the constantdelivery pump is 60 hp. Thus, since the sum of the maximum powers Qv Qc is equal to 160 hp. and higher than the power hp.) of the diesel engine 1, it is advisable to limit the sum of these powers to 120 hp. while permitting the free use by the pump 11 of the 20 hp. which, in any case, are never taken up by the pump 5 and represent the excess of power of the diesel engine 1 in relation to the maximum power of the pump 5. For this reason, the pressure-adjusted valve 47 is adapted to permit the passage of fluid in the pipe 43, from the pipe 17 to the restriction 41, when the pressure of fluid in the pipe 17, and consequently in the pipe 48, is greater than the pressure threshold at which the constant-delivery pump 11 takes up a maximum power of 20 hp. So long as the pressure in the pipe 17 is lower than or equal to the threshold corresponding to 20 hp, the pressure-adjusted valve 47 remains closed; the pressure in the chamber 33 is therefore zero, so that no power is subtracted from the maximum power liable to be taken up by the variable-delivery pump 5, this maximum power being equal to 100 h.p. On the other hand, when the pressure in the pipe 17 becomes higher than the threshold corresponding to 20 hp, the pressure-adjusted valve 47, controlled by the fluid in the pipe 48, opens and so enables the power regulator 19 to operate as described above with reference to FIGS. 1 to 4, and to enable the power necessary for driving the constant-delivery pump 11, which has to be driven with priority, to be subtracted from the maximum power of the 120 hp. diesel engine. Thus, if the power necessary for driving the pump 11 is equal to 60 hp, the regulator 19 will only leave a power of 120 hp. 60 hp. 60 hp. available at most to drive the variable-delivery pump.

It will be understood that in the above-described devices, the single variable-delivery pump 5 could be replaced by a group comprising a plurality of variabledelivery pumps. Such a modification is shown in the embodiment illustrated in FIG. 6 which comprises the identical variable-delivery pumps 5a and 5b, each of said pumps feeding, in the embodiment illustrated, a respective one of the hydraulic motors for driving the two caterpillar tracks of a public works machine. In the present case, the pumps 5a and 5b have identical characteristics, as have their respective power regulators 19a and 19b, in order to drive said tracks at the same speeds. The power regulators 19a and 19b each comprise two pistons 24ab and 24aa for the regulator 19a, and two pistons 24ba and 24bb for the regulator 19b, subjected to the sum of the effects of the fluid contained in the delivery pipes 14a and 14b of said two pumps. These power regulators are said to be of the pressure summation type. FIG. 7 represents a curve C of the variation, with a constant power, in the delivery Qv of one of the pumps 5a, 5b depending on the sum of the pressures Pva Pvb of the two pumps. Bearing in mind the identity of the supply circuits, the deliveries of the two variable-delivery pumps 5a and 5b are equal. It will be appreciated that the control circuit of each of the pumps 5a, 5b is similar to the control circuits of the pump 5, illustrated with reference to FIG. 5, the leakage flow passing through the restriction 41 being divided into two flows of half the value, which flow through the variable restrictions 34a and 34 b respectively. Similarly the action of the regulators 19a and 19b can be neutralised by the pressure-adjusted valve 47, when the sum of the maximum powers necessary for driving the two variable-delivery pumps 50 and 5b is lower than the maximum power of the engine 1, and the power necessary for driving the constant-delivery pump 11 is less than the difference between the maximum power of the engine 1 and the sum of the maximum powers of said pumps 5a and Sb.

In a modification, a single pump with a double body could replace the pumps 5a and 5b. Similarly, the supply principle which has been applied, may have other applications in the case where the corresponding de vices comprise more than two variable-delivery pumps. Moreover, different powers may be subtracted from the driving powers of a plurality of variable-delivery pumps, by regulating separately the value of the leakage flows passing through the corresponding variable restrictions of each regulator, particularly by modifying the section or the effective length of the grooves providing the restrictions. 1

Finally, it is possible to improve, in its turn, the supply device illustrated with reference to FIG. 6. An embodiment of supply device illustrated with reference to FIG. 8 provides at least one more constant-delivery supply during limited periods of time, the device supplying two additional circuits 53a and 53b. When the machine is being displaced in a straight line, the distributors 63a and 63b are disposed in their second position and constant-delivery pump 51 delivers to the reservoir 13, through pipes 58, part of 62b, 65, pressure-adjusted valve 59 and pipe 61.

When one of the utilization circuits, for example the circuit 53a, has to be supplied, the driver operates the pedal of distributor 63a, to bring the latter into its first position. The constant-delivery pump 51 delivers the fluid under pressure to the circuit 53a, through the pipe 58, the distributor 63a and pipe 64a. The supplying of the circuit 63a is then regarded as having priority. It is therefore necessary to subtract from the driving power of one of the variable-delivery pumps 5a or 5b, and in the present case from that of the pump 5a, a power equal to the driving power of said pump 51. This is why pipe 66a connects pipe 64a to the chamber 33a. For the sake of symmetry in the installation, the power necessary for driving the constant-delivery pump 51, when this is feeding the circuit 53b, is subtracted from the driving power for the variable-delivery pump 5b, by means of pipe 66b connecting pipe 64b to the chamber 33b. It is necessary to prevent the fluids from the pipes 66a or 66b from being conveyed through the restrictions 41a or 41b and thus disturbing the operation of the rest of the installation. For this reason, non-return valves 52a and 52b respectively are provided in the pipes 44aa and 44bb.

It will be noted that in this embodiment the constantdelivery pump 11 is associated with two laminar restrictions 41a and 41b. This arrangement enables separate regulation of the drops in pressure to be effected and consequently of the flows passing through each of these restrictions 41a and 41b and hence the maximum powers of the pumps 50 and 5b to be regulated to different values. The distributors 63a and 63b may have their separate or interconnected controls.

With the above described devices, the transfer of power from the translation circuit to the equipment circuit, or vice versa, is effected automatically by means of a regulating system taking into consideration the conditions of operation of the pump or pumps having a variable cubic capacity and equipment with constant power regulation (in the case of a plurality of pumps, this would be a regulation maintaining the power constant by summation of the operational pressures) and the conditions of operation of the pump having a constant cubic capacity.

The invention is not intended to be limited to the embodiments which have been described-but, on the contrary, covers all the modifications which may be made thereto, without departing from the spirit or scope of the invention.

What is claimed is:

l. A device for supplying fluid under pressure to at least two utilization circuits, each being connected to be supplied by a group of pumps comprising at least one pump and one delivery pipe, one of said groups of pumps being of the constant-delivery type, at least one other of said groups of pumps being of the variabledelivery type and having a member for controlling delivery thereof, the input shafts of the groups of pumps being connected to a single driving shaft, said supply device including:

a. at least one power regulator comprising a first jack having a piston;

b. means for rigidly connecting the cylinder of said first jack to the body of the pumps of said other groups;

c. means for coupling the piston of said first jack to said member for controlling the delivery of said other group;

d. a resilient member, said piston being subjected to the opposing actions of said resilient member and of the pressure of fluid in said delivery pipe of said other group of pumps;

e. a second jack having a piston;

f. means for rigidly connecting the cylinder of said second jack to the body of said pumps of said other p;

g. means for connecting the piston of said second jack to said member controlling the delivery of said other group, said piston delimiting with said cylinder of said second jack a chamber, said piston of said second jack being subject to the opposing actions of said resilient member and the pressure of fluid in said chamber;-

h. a connecting pipe, said chamber being connected to said delivery pipe of said one group of pumps by said connecting pipe;

i. a first laminar hydraulic restriction disposed in said connecting pipe; and

j. a second restriction, having a hydraulic resistance which is variable in dependence on the position of said piston of said second jack in its said cylinder, which connects said chamber with an enclosure at substantially zero pressure.

2. A device as claimed in claim 1, wherein a pressureadjusted valve is disposed in the connecting pipe between its connection to the delivery pipe of said one group of pumps and the laminar restriction, and is connected to be controlled by the pressure of the fluid in said delivery pipe.

3. A device as claimed in claim 1, wherein said laminar hydraulic restriction is adjustable and comprises a rod provided with a helical thread and movably disposed in a cylindrical bore, the rod being movable to vary the length of the threads in said bore.

4. A device as claimed in claim 1, wherein said second restriction comprises a groove in the cylindrical face of the piston of the second jack, a length of said groove which is variable in dependence on the position of said piston being disposed opposite the wall of the cylinder in which said piston is slidably mounted.

5. A device as claimed in claim 4, wherein said groove is helical.

6. A device for supplying fluid under pressure to at least three utilization circuits, each connected to be supplied by a group of pumps comprising at least one pump and one delivery pipe, one of said groups being of the constant-delivery type, and each of the other two groups being of the variable'delivery type, and having a member for controlling delivery thereof, the input shafts of the groups of pumps being connected to a single driving shaft, a first power regulator being connected to the member for controlling the delivery of a first of said other two groups of pumps, and a second power regulator being connected to the member for controlling the delivery of the second of said other two groups of pumps, each regulator comprising three jacks, having pistons and means for coupling the pistons of said jacks to said member for controlling the delivery of the corresponding group of pumps, the three jacks each delimiting a chamber for fluid. the effect of which is opposed to that of a resilient member, one of the chambers of each of the regulators communicating with the delivery pipe of one of the other two groups of pumps, another of the chambers of each of the regulators communicating with the delivery pipe of the other of the other two groups of pumps, and the third chamber of each of the regulators being connected by a connecting pipe to the delivery pipe of the one group of pumps, a first laminar hydraulic restriction being disposed in the connecting pipe, and two second restrictions, each having a hydraulic resistance which is variable in dependence on the position of a piston of each ofjacks, called second jacks, delimiting the third chambers, and connecting a respective one of the corresponding third chambers to an enclosure at substan-' tially zero pressure.

7. A device as claimed in claim 6, comprising a fourth utilization circuit adapted to be selectively connected to a second group of constant-delivery pumps, comprising at least one pump and one delivery pipe in which there is disposed a distributor having at least two positions for bringing said delivery pipe of the second group of pumps into communication, in one position, with said fourth utilization circuit by a secondary delivery pipe, and, in another position, with a fluid reservoir, a secondary connecting pipe connecting said secondary delivery pipe to the third chamber of one of the two regulators, and a non-return valve disposed in the connecting pipe connected to said third chamber, between the third chamber and the laminar restriction disposed in said connecting pipe, so as to permit the passage of fluid only from said laminar restriction to said third chamber.

8. A device as claimed in claim 6, wherein a pressureadjusted valve is disposed in each connecting pipe, be-' tween its connection to the delivery pipe of the one group of pumps and the laminar restriction, and is adapted to be controlled by the pressure of fluid in said delivery pipe.

9. A device as claimed in claim 6, wherein said laminar hydraulic restriction is adjustable and comprises a rod provided with a helical thread and movably disposed in a cylindrical bore, the rod being movable to vary the length of the threads in said bore.

10. A device as claimed in claim 6, wherein said sec ond restrictions each comprise a groove in the cylindrical face of the piston of the second jack, a length of said groove which is variable in dependence on the position of asid piston being disposed opposite the wall of the cylinder in which said piston is slidably mounted.

11. A device as claimed in claim 10, wherein each said groove is helical in shape.

UNTTTD STATES PATENT oTFIcE @ERHMQATE GE QGRREQTION Patent No. 3,859, 7990 Dated January 14, 1975 Inventor s Serge B, Gacquie et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading:

Insert Foreign Application Priority Data October 17, 1972 France .72 .36742 u'gncd and gtaled this fif Day 0? August 1975 [SEAL] A nest:

RUTH C. MASON C. MARSHALL DANN Alrvsling Officer ('mnmissimu'r uj'lau'nrs and Trademarks 

1. A device for supplying fluid under pressure to at least two utilization circuits, each being connected to be supplied by a group of pumps comprising at least one pump and one delivery pipe, one of said groups of pumps being of the constant-delivery type, at least one other of said groups of pumps being of the variable-delivery type and having a member for controlling delivery thereof, the input shafts of the groups of pumps being connected to a single driving shaft, said supply device including: a. at least one power regulator comprising a first jack having a piston; b. means for rigidly connecting the cylinder of said first jack to the body of the pumps of said other groups; c. means for coupling the piston of said first jack to said member for controlling the delivery of said other group; d. a resilient member, said piston being subjected to the opposing actions of said resilient member and of the pressure of fluid in said delivery pipe of said other group of pumps; e. a second jack having a piston; f. means for rigidly connecting the cylinder of said second jack to the body of said pumps of said other group; g. means for connecting the piston of said second jack to said member controlling the delivery of said other group, said piston delimiting with said cylinder of said second jack a chamber, said piston of said second jack being subject to the opposing actions of said resilient member and the pressure of fluid in said chamber; h. a connecting pipe, said chamber being connected to said delivery pipe of said one group of pumps by said connecting pipe; i. a first laminar hydraulic restriction disposed in said connecting pipe; and j. a second restriction, having a hydraulic resistance which is variable in dependence on the position of said piston of said second jack in its said cylinder, which connects said chamber with an enclosure at substantially zero pressure.
 2. A device as claimed in claim 1, wherein a pressure-adjusted valve is disposed in the connecting pipe between its connection to the delivery pipe of said one group of pumps and the laminar restriction, and is connected to be controlled by the pressure of the fluid in said delivery pipe.
 3. A device as claimed in claim 1, wherein said laminar hydraulic restriction is adjustable and comprises a rod provided with a helical thread and movably disposed in a cylindrical bore, the rod being movable to vary the length of the threads in said bore.
 4. A device as claimed in claim 1, wherein said second restriction comprises a groove in the cylindrical face of the piston of the second jack, a length of said groove which is variable in dependence on the position of said piston being disposed opposite the wall of the cylinder in which said piston is slidably mounted.
 5. A device as claimed in claim 4, wherein said groove is helical.
 6. A device for supplying fluid under pressure to at least three utilization circuits, each connected to be supplied by a group of pumps comprising at least one pump and one delivery pipe, one of said groups being of the constant-delivery type, and each of the other two groups being of the variable-delivery type, and having a member for controlling delivery thereof, the input shafts of the groups of pumps being connected to a single driving shaft, a first power regulator being connected to the member for controlling the delivery of a first of said other two groups of pumps, and a second power regulator being connected to the member for controlling the delivery of the second of said other two groups of pumps, each regulator comprising three jacks, having pistons and means for coupling the pistons of said jacks to said member for controlling the delivery of the corresponding group of pumps, the three jacks each delimiting a chamber for fluid. the effect of which is opposed to that of a resilient member, one of the chambers of each of the regulators communicating with the delivery pipe of one of the other two groups of pumps, another of the chambers of each of the regulators communicating with the delivery pipe of the other of the other two groups of pumps, and the third chamber of each of the regulators being connected by a connecting pipe to the delivery pipe of the one group of pumps, a first laminar hydraulic restriction being disposed in the connecting pipe, and two second restrictions, each having a hydraulic resistance which is variable in dependence on the position of a piston of each of jacks, called second jacks, delimiting the third chambers, and connecting a respective one of the corresponding third chambers to an enclosure at substantially zero pressure.
 7. A device as claimed in claim 6, comprising a fourth utilization circuit adapted to be selectively connected to a second group of constant-delivery pumps, comprising at least one pump and one delivery pipe in which there is disposed a distributor having at least two positions for bringing said delivery pipe of the second group of pumps into communication, in one position, with said fourth utilization circuit by a secondary delivery pipe, and, in another position, with a fluid reservoir, a secondary connecting pipe connecting said secondary delivery pipe to the third chamber of one of the two regulators, and a non-return valve disposed in the connecting pipe connected to said third chamber, between the third chamber and the laminar restriction disposed in said connecting pipe, so as to permit the passage of fluid only from said laminar restriction to said third chamber.
 8. A device as claimed in claim 6, wherein a pressure-adjusted valve is disposed in each connecting pipe, between its connection to the delivery pipe of the one group of pumps and the laminar restriction, and is adapted to be controlled by the pressure of fluid in said delivery pipe.
 9. A device as claimed in claim 6, wherein said laminar hydraulic restriction is adjustable and comprises a rod provided with a helical thread and movably disposed in a cylindrical bore, the rod being movable to vary the length of the threads in said bore.
 10. A device as claimed in claim 6, wherein said second restrictions each comprise a groove in the cylindrical face of the piston of the second jack, a length of said groove which is variable in dependence on the position of asid piston being disposed opposite the wall of the cylinder in which said piston is slidably mounted.
 11. A device as claimed in claim 10, wherein each said groove is helical in shape. 